It's necessary for students to be able to explain what they know and how they know it. In this case, I asked the students to reflect on their experience about which cart had the most potential or kinetic energy. While this student didn't articulate his thoughts in the most grammatically correct format, he was able to tell me that objects that are higher have more potential energy and he knew this because of the calculated speed.

Big Idea:
Students find out that the height of an object effects its mechanical energy by using carts and ramps.

This lesson is designed to engage students in scientific discourse around mechanical energy and an object's position. By experimenting and collecting data, students will be able to provide evidence for their claims, thus addressing standard SP7 and MS-PS3-2 simultaneously.

Resources (2)

Resources

For the next section, I use the PhEt demonstration used in the prior lesson, Mechanical Energy and Mass. If each of your students have access to a device with flash, they can run the demo themselves. Because we use iPads in the classroom, they do not have flash, and so I run the demo using my laptop and the SMARTBoard.

While observing the demonstration, I ask students to answer the following questions in order to guide their thinking:

Where does the skater have the MOST potential energy?

Where does the ball have the MOST potential energy?

Which, skater or ball, had more speed while moving down the ramp?

Why do you think this?

After the demo is run, I give the kids an additional 3-4 minutes to finish writing down their thoughts in their notes sheets. Then, I ask the kids to share their answers with their shoulder partners (person sitting closest to their right shoulders) and compare responses.

Now, students will actually test their thinking by doing a hands on activity using the carts and ramps. To do the activity, you will need the following materials per team: 1 cart, 1 ramp, tape, measuring tape, calculator.

Students follow the procedure on their notes sheet and record their data (distance travelled, time it took) and calculate the speed for each release point.

I am moving around from group to group ensuring proper following of the procedure and also asking questions like:

What have you noticed so far about the different release points?

Has the car moved faster or slower as you move the release point higher?

Resources (1)

Resources

After the activity, it's important for students to use this data to help them form their thinking about mechanical energy and position. To do this, I have them answer the following questions in their notes sheet:

Which cart had the most potential energy? How do you know?

Which cart had the most kinetic energy? How do you know?

By increasing (making more) the height of the cart, what did you do to the amount of mechanical energy?

It's important for students to include evidence from their activity and from the demonstration to support their answers. This will help to address SP7 and also make them better writers because the are practicing supporting their thoughts with concrete examples and evidence.